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Finally, if this is about random ordering and you're hosted with WP Engine, you need to specifically activate "Allow ORDER BY RAND()" in WordPress Admin > WP Engine, General Settings tab.
Still Stuck? Let's Reset
This is probably related to having a large between plugin updates. To get fixed quickly, let's get back to the most common working scenario by resetting the global Testimonials settings and redoing widgets. Screenshots are below.
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At this point if testimonials are displaying correctly, then change one widget, shortcode, or global option at a time and notice the effects. Please recall that once you create a widget, global settings don't affect widgets.
WordPress Admin > Testimonials > Settings, Reset tab
WordPress Admin > Appearance > Widget > your testimonials widget, Reset options section
